Sometimes I don't know what the "/" means in Prolog

I see slashes used like this in code:

solution([X/Y|Others]) :-
   noattack(X/Y, Others).

But then sometimes I see "/1" "/2" etc. in Prolog.

What do these statements (characters) mean?

Solution

In both your examples it's used as infix operator, but with different, unrelated, meaning.

In the first rule you cite it's just a separator, as Mog already pointed out. The other use, mostly for documentation purposes, it's as predicate indicator. Useful because we can have different predicates with the same functor.

Expressions are just syntax sugar for binary or unary relations, where the functor is an operator. The meaning of such expressions is defined by context: for instance, is/2 takes care of arithmetic evaluation of expressions: here the operator performs the expected arithmetic operation

?- X is 10 / 3.
X = 3.3333333333333335.

The builtin current_op allows inspecting operators' definitions. Try

   ?- current_op(Precedence,Associativity,/).
   Precedence = 400,
   Associativity = yfx .

We can have a predicate named /. A silly example:

/(A, B) :- format(A, B).

or better

A / B :- format(A, B).

could be used as a shorthand where we have many format(s). This usage is discouraged, leading to hard to read programs, but given such definition, this is a valid rule:

?- 'hello ~s' / [world].
hello world